Chem Questions (1 Viewer)

[Jumbo Cactuar]

2HCl + Ba(OH)₂ -----> BaCl₂ + 2H₂0

n_Ba(OH)2 = C*V

= 0.2*0.02
= 0.004 mol

n_HCl = 2 * 0.004 = 0.008 = C*V

C = 25M
V = 0.008/25 = 0.00032L = 0.32mL

I wonder what the error on that titration is.

@xiao1985: I was after concentration is related to amount of light absorbed.

Absorbance is a negative log scale of transmittance. Absorbance is proportional to concentration. ( beer's law : absorbance = epsilon(constant) * pathlength * concentration)

 

[nit]

this is a kind of useless game since the hsc chem exam mainly consists of the dot-points expressed as questions - none of this rephrasing of dot-points which would actually require some understanding

 

[Emma-Jayde]

All in the name of science my friend!
We're enjoying ourselves, and we haven't hurt anyone yet!

 

[shafqat]

nit's just bitter he wasn't able to dominate the hsc with his amazing chem skills

 

[Emma-Jayde]

Anyhooo, to another question then...

Describe the differences between the alkanol and alkanoic acid functional groups in carbon compounds

 

[Dreamerish*~]

Anyhooo, to another question then...

Describe the differences between the alkanol and alkanoic acid functional groups in carbon compounds

an alkanol is a compound which contains an OH group attached to a C atom that only has C or H atoms attached to it. the compound consists of only C, O and H atoms. it has the general formula C_nH_{2n + 2}.
an alkanoic acid is a compound which consists of the functional group COOH, which is a C atom forming a double bond with an O atom, and a single bond with an OH group. it has the general formula C_nH_2nO₂ with n>0.

 

[Jumbo Cactuar]

^^ Alkanoic tends to be stronger acid since double bonded O draws electron density from OH, affecting a weaker OH bond.

Ahahh I have another question! Much easier this time!

At standard conditions HCl has a maximum solubility of 70g per 100g of water.

Assuming that this dissolution accompanies no change in volume of the solvent, prove that Budz should think before he posts

PS: this is a serious question here!

 

[Emma-Jayde]

Let x = 1 = Budz
Let y = 1 = max solubility of HCl

As x = 1 and y = 1,
x = y

Multiplying both sides by x
x² = xy

Subtracting y² from both sides:
x² - y² = xy - y²

Factorising:
(x+y)(x-y) = y(x-y)

Dividing both sides by (x-y)
x + y = y

Substitution given information:
1 + 1 = 1

As this is obviously not true, Budz (and everyone else) should think before they post!!!

 

[Jumbo Cactuar]

Don't mock my question! The question is 'what is saturated HCl' ?

 

[Emma-Jayde]

I'm sorry, I couldn't resist the temptation!

HCl is a solution of the acidic Hydrogen Chloride gas in water. A saturated solution is one in which no more of the solute (HCl) will be dissolved by the solvent (water).

 

[Jumbo Cactuar]

........ and? Think quantitatively not qualitatively!

First line:
[HCl] = m / ( M * V)

 

[Emma-Jayde]

With 70% solubility the highest concentration you could get would be 9.735molL^-1

 

[Jumbo Cactuar]

Nice try;

V = 0.1L (1kg = 1L)
m = 70g
M = 35.45 + 1.008 = 36.53g/mol

[HCl] = m / ( M * V)
= 70 / 36.53*0.1
= 19.2 Molar

Which sounds reasonable since I've only seen as high as 18M. Budz' question talks of 25M HCl reacting with 0.2M Ba(OH)2 ~ which is very silly indeed!

 

[Emma-Jayde]

My bad...I added 35.45 with 1.008 and got 71.908.
Hmmm typo because I was using my phone and not my calculator

 

[Budz]

Ahh.. lol
sorry didnt realise